Devices for ascertaining whether a railroad switch is open have been used in association with switch mechanisms for many years in railroad yards, hump yards and on mainlines; however such devices have not been used to control heating at a switchpoint.
Heat at the switchpoint is required to prevent freezing and accumulation of snow and ice preventing the switch from moving when desired. Where a switch is frozen, or snow or ice interferes with the opening or closing of the switch, there is great danger of derailment, causing substantial loss of persons or property.
Many means have been used to keep a switchpoint free of ice and snow. For many years, trackmen have been known to set fires at the switchpoint during storms to prevent snow and ice buildup which if allowed to accumulate may prevent movement of the switch, but also may cause a false reading showing the switchpoint to be closed when it is really open. Gas heaters are also available with heating nozzles for applying heat at the switchpoints. The more modern means to prevent snow and ice build-up is to install a heating element or Calrod on the stockrail at the switchpoint. During a storm, these heating element are turned on and left on until the danger of snow or ice build-up is over, even when the switch is fully closed as intended and heat is not required. When sophisticated equipment is available for detecting whether a switchpoint is open or closed and there is high energy equipment for applying heat to the switchpoint during a storm, and the control may be in a tower remote from the switch, and a whole maze of detectors and controls is in a train make-up yard where there may be many switchpoints, the system becomes rather complicated and the possibility of human error increases with very high stakes.
However, even with such sophisticated equipment, railroads suffer derailments. Many derailments can be traced to conventional mechanisms for detecting whether a switch is open or closed. Such prior art mechanisms are usually of a type which detect an obstructed open switch point, but only if the obstruction results in mechanical pressure directed against the switch machine. If there is no obstruction, the detector mechanism may cause an erroneous reading. Likewise, conventional wisdom is to apply heat to the entire switchpoint, irrespective of localized needs, thus wasting energy and losing efficiency.
Many switches in the railway industry are manually operated, usually because the switch is remote from a source of adequate electricity or track use doesn't justify the cost of installing electric switches. That factor also reflects conventional thinking about the availability of power to heat the switchpoint, where conventional heating elements are about 16 ft. long and normally consume about 480 volts of electricity.
Such manually operated switches are usually located in areas where trains loaded with hazardous materials and chemicals and other critical cargos travel. Frequently, derailments at such locations are caused by open switchpoints, usually because of human error or failure to notice that the switchpoint is safely closed against the stockrail during operations in bad weather or without visibility. Also, such manually operated switches are usually in locations where switch service is not so effective, making it easier to miss mistakes in calibrations or settings leading to a false belief that a switchpoint is closed when in fact it is open. The use of an electric switch or heater in these circumstances could prove valuable if energy requirement were not burdensome.
Sometimes stop signs and similar devices are mechanically attached to manually operated switch gear boxes, which are designed only to indicate which route the switch is directed to and not to whether the switchpoint is open or closed. False reliance on these devices, coupled with a switchman's conception of the switch condition, usually under pressure to throw another switch keeping the train moving, leads the switchman to assume the switchpoint is in the position designated because the switch lever has dropped inside the lever slot, without inspection of the switchpoint.
Even with powered switches in hump or switch yards with sophisticated equipment derailments are not infrequent and are often disastrous when they occur. Investigation sometimes reveals an obstruction at the switchpoint, or misadjustment or worn out movable parts and mechanical components, sometimes just a light bulb. Such failures may be traced to loose or worn out movable parts and mechanical components, poor maintenance, loose ballast conditions, loose stockrail braces, worn out or loose throwrod adjusting nuts, baskets, or broken throwrods, worn out or broken lugs connecting the switch sectors and throwrods, or just the inability to have adequate heat at the right location to keep the switchpoint free of ice, slush and snow.
Sometime derailment is caused by human error because the sun light was too bright to see the safety light in the field or a obstructed switchpoint. In these situations the "clear" safety signal indication, either in the tower or on the field, may be false and can be the direct cause of derailment. Operating personnel sometimes can't see a faulty switchpoint in time to take action avoiding a derailment, because a light is burned out or there is glare, or darkened conditions or obstructions.
Failure can be traced to prior art detectors, adjusted and set according to calibrations, rather than a positive relationship between the stockrail and the switchrail at the point where they are intended to come together or be separated. Even if a conventional detector is initially properly calibrated, changes occur which make the calibration inaccurate or obscure the detector. If the calibration is changed by conditions which are not regularly ascertained and checked, sometimes by a misalignment of merely 0.05 inch, such as movement of the tracks, detector or switch components relative to one another, which may result from vibrations of a locomotive or rolling stock over the track or a change in weather, a derailment may result. Power may also be interrupted or a warning source obliterated or inoperative--any of which can cause a derailment. Any of these conditions, including insufficient heat at the switchpoint may cause conditions which could be better dealt with by the present invention.